Cruise ships’ smokestacks may soon be spewing less toxic pollution into the New York air, thanks to Con Ed’s deal for an electric rate increase next year.

It is currently cheaper for the ships to make electricity with their own high-pollution, diesel-powered generators than to use power from shore. The proposed rate plan, now before the state Public Service Commission, could make it less expensive for the ships to plug in to Con Ed’s grid.

The utility would negotiate cruise-ship power rates with the city, which runs the Brooklyn terminal in Red Hook with the Port Authority and Manhattan’s West Side terminal with a private contractor.

Ships use a grade of diesel that spews more carcinogens and toxic chemicals than the one used by trucks and trains.

“Ships in port basically idle, and they idle 24 hours a day,” said community activist Adam Armstrong, who has pushed for stricter antipollution rules at the Brooklyn terminal, which opened in 2006.

He estimates that fuel used by the Princess and Carnival ships docked in Red Hook is 90 times dirtier than diesel truck fuel.

“It’s like 14,000 cars idling at the end of our street,” he said. “You can’t really smell it . . . It looks cleaner than it actually is.”

US ports have been slow to let ships plug in to power on shore. New York’s cruise terminals would be the only ones on the East Coast to offer shore power.